[Gmsh] .step file editing

[Christophe Geuzaine]

Hi Marco,

Yes, you can edit STEP files: see e.g. https://gitlab.onelab.info/gmsh/gmsh/blob/master/demos/boolean/import2.geo <https://gitlab.onelab.info/gmsh/gmsh/blob/master/demos/boolean/import2.geo>. Notice the "SetFactory("OpenCASCADE") line at the beginning of the .geo file, which means that the STEP file will be imported as an OpenCASCADE model - we then provide all the classical functionalities to modify the resulting shapes (deleting parts, applying transformations and boolean operations, etc.), directly in the .geo file.

What we never do is translate between CAD kernels: so you will never be able to "export" to the native GEO geometry kernel (this kernel does not know about many of the geometrical primitives in the STEP format). You directly work with the native CAD representation of the geometry (here with OpenCASCADE). Future releases of Gmsh will provide the same kind of functionality with other CAD kernels, like Parasolid.

To export a "dead" (non parametric) version of your geometry, you should use the native "dead" format of the underlying CAD kernel. With OpenCASCADE, you just export as a BREP file, i.e. by adding

Save "output.brep";

in your .geo file.

Christophe


> On 14 May 2018, at 16:15, Marco Tiberga <M.Tiberga at tudelft.nl> wrote:
> 
> Dear GMSH developers,
>  
> I was looking into the GMSH reference manual to see whether it is possible to read .STEP files, to edit them, and/or to export them to .geo format.
> I guess that the FAQ 4 in Appendix E.4 answers my questions.
>  
> However, it is not clear to me whether we can or not delete entities, after merging a .STEP file into a .geo one (this feature is both indicated as something already available and something coming in a later release).
> Also, I was wondering whether the possibility export .STEP files to .geo format is actually something coming in the near-future releases or later.
>  
> Thanks a lot for the clarification.
>  
> Best regards,
>  
> Marco Tiberga
> PhD candidate
> Delft University of Technology
> Faculty of Applied Sciences
> Radiation Science & Technology Department
> Mekelweg 15, 2629 JB Delft, The Netherlands
> E-Mail: m.tiberga at tudelft.nl <mailto:m.tiberga at tudelft.nl>
> Website: http://www.nera.rst.tudelft.nl/ <http://www.nera.rst.tudelft.nl/>
>  
>  
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